Equine Influenza


What is Equine Influenza? 

Equine Influenza is a highly contagious though rarely fatal respiratory disease. The virus is distinct from influenzas viruses in other species. The most common form of transmission is airborne droplets in  from affected horses. 

Clinical Signs: The clinical signs for equine influenza are the following:

  • Fever up to 106 degrees, lethargy, anorexia, muscle pain/weakness 
  • Dry, harsh to hacking cough usually proceeds fever. Cough can last up to 6 weeks after all other clinical signs have abated.
  • Nasal discharge is initially serous (clear and watery) but occasionally may become mucopurulent (yellow or white) with secondary bacterial infections. 
  • Secondary bacterial infections are common in horses with influenza 
  • Slightly enlarged and mildly painful lymph nodes around the head and neck area 
  • May be more severe in donkeys and mules 
  • Rarely, clinical signs can include distal limb edema (swelling of the lower legs) and cardiomyopathy (decreased heart function). 

Diagnosis: Equine influenza is diagnosed by virus isolation from nasal swabs, through PCR testing by nasal swab and using an ELISA (enzyme-linked immunosorbent assay). Diagnosis can also be made by sampling during the acute and convalescent stage of the disease to detect an increase in antibodies.

Treatment: Supportive care and rest are the chief treatments. 

Prevention: Isolation and increased biosecurity for 14 days after the clinical signs are resolved.


July 03, 2024
Simcoe County, ON
Confirmed Case(s) - Voluntary Quarantine
June 21, 2024
Madison County, AL
Confirmed Case(s) - Voluntary Quarantine
May 20, 2024
Clallam County, WA
Confirmed Case(s) - No Quarantine